• To determine the clinical and functional characteristics of isolated platelet factor 3 (PF-3) deficiency, platelet function studies were carried out in 316 patients who were suspected of having a bleeding tendency. Although PF-3 abnormality was observed in 69 patients (22%), an isolated PF-3 abnormality was noted in only three patients. The abnormality was congenital in one patient and secondary to Hashimoto's thyroiditis, Ehlers-Danlos syndrome, and chronic myelocytic leukemia in the other two. Further investigations in the patient with congenital abnormality disclosed that PF-3 activity failed to respond to any of the stimuli tested, and there was a clear dissociation between PF-3 availability and platelet aggregation. The abnormality was due to an intrinsic platelet defect caused by a true deficiency of the membrane phospholipid clotting activity. The findings clearly establish that isolated PF-3 deficiency is an entity of qualitative platelet disorders that may be associated with a severe bleeding tendency.
(Arch Intern Med 140:366-367, 1980)